linux-kernel - Re: [PATCH v1 1/2] iio: core: Leave private pointer NULL when no private data supplied

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Message-ID: <20240309183700.60133d78@jic23-huawei>
Date: Sat, 9 Mar 2024 18:37:00 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, Lars-Peter Clausen
 <lars@...afoo.de>
Subject: Re: [PATCH v1 1/2] iio: core: Leave private pointer NULL when no
 private data supplied

On Mon,  4 Mar 2024 16:04:32 +0200
Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:

> In iio_device_alloc() when size of the private data is 0,
> the private pointer is calculated to point behind the valid data.
> Leave it NULL when no private data supplied.
> 
> Fixes: 6d4ebd565d15 ("iio: core: wrap IIO device into an iio_dev_opaque object")
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

Fix is a strong word given any driver trying to access the pointer in this case
will be broken anyway.  I don't mind it being backported as it'll make bugs
easier to identify but I'm not rushing it in.

Otherwise seems like a sensible bit of tidying up.

Jonathan

> ---
>  drivers/iio/industrialio-core.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index 4302093b92c7..8684ba246969 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -1654,8 +1654,10 @@ struct iio_dev *iio_device_alloc(struct device *parent, int sizeof_priv)
>  		return NULL;
>  
>  	indio_dev = &iio_dev_opaque->indio_dev;
> -	indio_dev->priv = (char *)iio_dev_opaque +
> -		ALIGN(sizeof(struct iio_dev_opaque), IIO_DMA_MINALIGN);
> +
> +	if (sizeof_priv)
> +		indio_dev->priv = (char *)iio_dev_opaque +
> +			ALIGN(sizeof(*iio_dev_opaque), IIO_DMA_MINALIGN);
>  
>  	indio_dev->dev.parent = parent;
>  	indio_dev->dev.type = &iio_device_type;